Rewrite FetchDefinedStages and BuildQuickSyncStages with plugin SDK (… #1430

Job	Run time
artifacts (ghcr.io/pipe-cd, helloworld)	2m 7s
artifacts (ghcr.io/pipe-cd, launcher)	2m 23s
artifacts (ghcr.io/pipe-cd, launcher-okd)	2m 24s
artifacts (ghcr.io/pipe-cd, pipecd)	4m 25s
artifacts (ghcr.io/pipe-cd, piped)	3m 44s
artifacts (ghcr.io/pipe-cd, piped-okd)	3m 51s
artifacts (ghcr.io/pipe-cd, pipectl)	1m 51s
artifacts (gcr.io/pipecd, helloworld)	2m 5s
artifacts (gcr.io/pipecd, launcher)	2m 13s
artifacts (gcr.io/pipecd, piped)	4m 8s
trigger-event-watcher	7s
release-quickstart-manifests	0s
	29m 18s

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